1. Field of the Invention
The invention relates to a steering system.
2. Description of the Related Art
A steer-by-wire system has been proposed in which a steering member and a steering operation mechanism are not mechanically coupled together and in which a steering angle of a steering wheel is detected by an angle sensor so that a driving force exerted by a steering operation actuator controlled in accordance with a sensor output from the angle sensor is transmitted to the steering operation mechanism (see, for example, Japanese Patent Application Publication No. 2013-132950 (JP 2013-132950 A)). On the other hand, when the steer-by-wire system is mounted in a vehicle, an appropriate measure needs to be taken so that steered wheels can be steered even when the steering operation actuator or the like becomes defective.
Japanese Patent No. 4927608 and Japanese Patent No. 4347100 disclose, as a steering system for which the above-described measure has been taken, a configuration in which the steering member and the steering operation mechanism are coupled together via a clutch mechanism and in which the steering member and the steering operation mechanism are mechanically uncoupled from each other during a normal operation and are mechanically coupled together when an abnormality occurs.
When mounted in the steering system, a clutch mechanism may be, for example, interposed between an intermediate shaft and a steering column. However, in this case, the clutch mechanism may interfere with peripheral members. The steering system in which the clutch mechanism is mounted is desirably restrained from being increased in size.